Washington -LRB- CNN -RRB- -- What may be the most contentious Pentagon contract is the focus of yet another fight , with this round centered on whether a bid for a $ 35 billion contract should be thrown out because it arrived five minutes late .

For about a decade the Air Force has been trying to replace its fleet of KC-135 air refueling tankers , the big jets that act as flying gas stations for warplanes .

In the latest attempt , three companies wanted to submit bids to build the KC-X , the next generation of tankers ; Boeing , EADS and US Aerospace .

Each company 's bid was required to be submitted to an office at Wright-Patterson Air Force Base in Dayton , Ohio , by 2 p.m. July 9 .

Boeing and EADS got their bids into the office with time to spare . US Aerospace said its bid arrived at Wright-Patterson half an hour before the deadline . The Defense Department said it was five minutes late .

US Aerospace is a new company that is in partnership with Antonov , a state-owned Ukrainian aircraft manufacturer that used to build planes for the Soviet Union 's military and now specializes in building very large aircraft .

Because of the late arrival of the bid , the Defense Department will not consider US Aerospace 's proposal , according to Pentagon chief spokesman Geoff Morrell .

`` We are not allowed by law to even review their proposal . It did not arrive in time . So we can not consider it . We can not review it , '' Morrell said .

A spokesman for US Aerospace , Chuck Arnold , said the Defence Department `` still feel -LSB- s -RSB- the cold war is on '' and does n't want US Aerospace to succeed in the bid .

Morrell said the rules are clear .

`` This is a $ 30 billion to $ 40 billion contract . That is not a high school homework assignment , OK ? These deadlines count , and any professional contractor understands that , '' he said .

Chuck Arnold , a spokesman for US Aerospace , said the bid proposal was on time .

`` We have documented evidence that the messenger -LSB- who was carrying the bid -RSB- was there at 1:30 . '' But Wright-Patterson is a huge facility and the company said the messenger was held up at the gate , then got lost driving to the building where the bid needed to be . When the messenger and the bid proposal finally arrived at the proper location , the bid was marked as having arrived at 2:05 .

The company was told the bid would not be considered .

US Aerospace is fighting that decision and asking that its bid proposal , which it said will save U.S. taxpayers millions of dollars and produce a better tanker plane , be considered .

That might mean further delay in a process that began in 2002 and has been stopped and restarted twice . Morrell said he is confident that the dispute with US Aerospace will not slow the process again .

`` Are we concerned about their protest that it might lead to a delay in the awarding of this contract ? I do n't believe so , '' Morrell said . `` This is going on . We will -- we will award this contract in the fall , as we always said we would . ''

@highlight

Contact to build air refueling tankers is worth $ 30-40 billion

@highlight

Ukrainian aircraft manufacturer 's bid will not be accepted

@highlight

Messenger gets to air base gate on time , but not to the office to deliver bid